Decorative marking films are widely used outdoors or indoors as substitution material for painting. Materials having excellent adhesion property over various temperature ranges from winter to summer are desired. Generally, acrylic polymers having good outdoor durability are used.
In some references, the adhesive composition comprises a resin composition is disclosed. A first resin composition was obtained by copolymerizing monomers consisting essentially of alkyl (meth)acrylate, and further containing 0.5-10 wt. % unsaturated monomer having a carboxyl group and copolymerizable with the 1-12C alkyl (meth)acrylate, and having ≧800,000 weight average molecular weight. This was then mixed with a second resin composition obtained by copolymerizing monomers consisting essentially of one or more kinds of monomers selected from a 1-20 C alkyl methacrylate, a cycloalkyl methacrylate, benzyl methacrylate or styrene, and further containing 0.5-10 wt. % copolymerizable unsaturated monomer having an amino group, and having ≦40° C. glass transition temperature and ≦100,000 weight average molecular weight. About 1-40% by weight of the second resin composition was added to 100 parts weight of the first resin composition. See, for example, JP 3516035B.
An adhesive composition for a hot melt adhesive comprising a mixture of a copolymer consisting of carboxylic group-containing acrylic acid ester and a copolymer consisting of amines was disclosed in, for example, JP 54-88938 A.
Further an adhesive composition suitable for optical products comprising a blend of a pressure sensitive adhesive, a polymer having a weight average molecular weight of over 100,000 and a high Tg, and a crosslinker was disclosed in, for example, JP 2006-522856 T.
An adhesive composition comprising a tacky polymer, a low molecular weight polymer and a crosslinker was also disclosed. The tacky polymer had a weight average molecular weight of more than 600,000 consisting essentially of alkoxyalkyl(meth)acrylate with a carboxyl group-containing monomer, and the low molecular weight polymer had a glass transition temperature (Tg) of more than 60 degrees C. and a weight average molecular weight of less than 50,000. See, for example, JP 2002-327160 A.
Generally, an adhesive composition having good adhesion at low temperatures in winter is difficult to adhere initially due to a high initial tack at ambient or higher temperature. A monomer having a high glass transition temperature (Tg) can be used to reduce the initial tack. In this case, another issue such as an adhesion property in low temperature comes up. A non-adhesive component such as inorganic materials or plasticizers can be dispersed to the tacky polymer, but it is still problem that an adhesion property at low temperature decreases or an adhesion property is impaired by migrating of additives to the surface.